/*
 * <copyright>
 *
 *  Copyright 1997-2007 BBNT Solutions, LLC
 *  under sponsorship of the Defense Advanced Research Projects
 *  Agency (DARPA).
 *
 *  You can redistribute this software and/or modify it under the
 *  terms of the Cougaar Open Source License as published on the
 *  Cougaar Open Source Website (www.cougaar.org).
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 *  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * </copyright>
 */
/*
 NaturalOrderComparator.java -- Perform 'natural order' comparisons of strings in Java.
 Copyright (C) 2003 by Pierre-Luc Paour <natorder@paour.com>

 Based on the C version by Martin Pool, of which this is more or less a straight conversion.
 Copyright (C) 2000 by Martin Pool <mbp@humbug.org.au>

 This software is provided 'as-is', without any express or implied
 warranty.  In no event will the authors be held liable for any damages
 arising from the use of this software.

 Permission is granted to anyone to use this software for any purpose,
 including commercial applications, and to alter it and redistribute it
 freely, subject to the following restrictions:

 1. The origin of this software must not be misrepresented; you must not
 claim that you wrote the original software. If you use this software
 in a product, an acknowledgment in the product documentation would be
 appreciated but is not required.
 2. Altered source versions must be plainly marked as such, and must not be
 misrepresented as being the original software.
 3. This notice may not be removed or altered from any source distribution.
 */
package org.swrlapi.factory;

import org.checkerframework.checker.nullness.qual.NonNull;

import java.util.Comparator;

public final class NaturalOrderComparator<T> implements Comparator<T>
{
  @NonNull public static final Comparator<String> NUMERICAL_ORDER = new NaturalOrderComparator<>(false);
  @NonNull public static final Comparator<String> CASE_INSENSITIVE_NUMERICAL_ORDER = new NaturalOrderComparator<>(true);

  private final boolean caseInsensitive;

  private NaturalOrderComparator(boolean caseInsensitive)
  {
    this.caseInsensitive = caseInsensitive;
  }

  private int compareRight(@NonNull String a, @NonNull String b)
  {
    int bias = 0;
    int ia = 0;
    int ib = 0;

    // The longest run of digits wins. That aside, the greatest
    // value wins, but we can't know that it will until we've scanned
    // both numbers to know that they have the same magnitude, so we
    // remember it in BIAS.
    for (; ; ia++, ib++) {
      char ca = charAt(a, ia);
      char cb = charAt(b, ib);

      if (!Character.isDigit(ca) && !Character.isDigit(cb)) {
        return bias;
      } else if (!Character.isDigit(ca)) {
        return -1;
      } else if (!Character.isDigit(cb)) {
        return +1;
      } else if (ca < cb) {
        if (bias == 0) {
          bias = -1;
        }
      } else if (ca > cb) {
        if (bias == 0)
          bias = +1;
      } else if (ca == 0 && cb == 0) {
        return bias;
      }
    }
  }

  @Override public int compare(@NonNull T o1, @NonNull T o2)
  {
    String a = o1.toString();
    String b = o2.toString();

    int ia = 0, ib = 0;
    int nza, nzb;
    char ca, cb;
    int result;

    while (true) {
      // only count the number of zeroes leading the last number compared
      nza = nzb = 0;

      ca = charAt(a, ia);
      cb = charAt(b, ib);

      // skip over leading zeros
      while (ca == '0') {
        if (ca == '0') {
          nza++;
        } else {
          // only count consecutive zeroes
          nza = 0;
        }

        // if the next character isn't a digit, then we've had a run of only zeros
        // we still need to treat this as a 0 for comparison purposes
        if (!Character.isDigit(charAt(a, ia + 1)))
          break;

        ca = charAt(a, ++ia);
      }

      while (cb == '0') {
        if (cb == '0') {
          nzb++;
        } else {
          // only count consecutive zeroes
          nzb = 0;
        }

        // if the next character isn't a digit, then we've had a run of only zeros
        // we still need to treat this as a 0 for comparison purposes
        if (!Character.isDigit(charAt(b, ib + 1)))
          break;

        cb = charAt(b, ++ib);
      }

      // process run of digits
      if (Character.isDigit(ca) && Character.isDigit(cb)) {
        if ((result = compareRight(a.substring(ia), b.substring(ib))) != 0) {
          return result;
        }
      }

      if (ca == 0 && cb == 0) {
        // The strings compare the same. Perhaps the caller
        // will want to call strcmp to break the tie.
        return nza - nzb;
      }

      if (ca < cb) {
        return -1;
      } else if (ca > cb) {
        return +1;
      }

      ++ia;
      ++ib;
    }
  }

  private char charAt(@NonNull String s, int i)
  {
    if (i >= s.length()) {
      return 0;
    } else {
      return this.caseInsensitive ? Character.toUpperCase(s.charAt(i)) : s.charAt(i);
    }
  }
}
